Phase Transition Research Articles

Gearing of nitrate ions in ammonium nitrate.

Reorienting polyatomic ions such as NH4+ and NO3- exhibit weak magnetic fields because the ions at the extremities trace out current loops; if the periodic reorientations become long-range ordered (i.e., gearing of neighboring NO3-), then the magnetic susceptibility should exhibit a unique signature along the different crystallographic axes. For the case of ammonium nitrate (NH4NO3), we report the presence of two successive sharp steps in the molar magnetic susceptibility along the a- and b-axes upon crossing its order-disorder phase transition (from phase IV to phase II). We suggest that the first step pertains to the NO3- planes shifting away from facing only along the b-axis and onto the a-axis by 45°. The second step is attributed to the disordering (ungearing) of the NH4+ and NO3-. In contrast, only one step was observed in the magnetic susceptibility along the c-axis, and its large magnitude suggests that the NO3- remain weakly correlated even in phase I at 400K. We also find evidence that the NH4+ become magnetically ordered (geared) along the c-axis only until phase V. The approach employed in this work can be extended to experimentally study the lattice dynamics of other solids possessing planar ions such as amphidynamic crystals.

Mechanisms of Enhanced Electrochemical Performance by Chemical Short-Range Disorder in Lithium Oxide Cathodes.

LiCoO2 has been one of the dominant cathode materials commercially used in rechargeable lithium-ion batteries, while the performance is severely limited by its low reversible capacity (∼140 mAh/g), primarily due to the destructive phase transitions at high voltages (>4.2 V vs Li/Li+), leading to structural degradation and rapid decay of capacity. A recent experimental study [Wang et al. Nature 2024, 629, 341] showed that chemical short-range disorder (CSRD) in LiCoO2 can effectively prevent phase transitions and structural deterioration. To better understand the underlying mechanisms, we carry out a theoretical study on CSRD-based LiCoO2 by performing ab initio molecular dynamics simulations accelerated by machine learning and find that CSRD effectively suppresses phase transitions from hexagonal to monoclinic at Li0.5CoO2 and from O3 to H1-3 at Li0.25CoO2. The enhanced phase stability is attributed to the reduced lattice variation in the c-axis, the increased oxygen vacancy formation energies, the higher oxygen dimer formation energies, and the stabilization of Co atoms in the Li layers during delithiation. The high Li+ diffusion coefficients are found to arise from the low-barrier 0-TM diffusion channels and an expanded diffusion network from 2D to quasi-3D induced by CSRD. Furthermore, CSRD narrows the band gap of LiCoO2 with enhanced electronic conductivity, driven by the changes in the Co valence state and the introduction of linear Li-O-Li configurations. Equally important, CSRD can also enhance the stability of Li-rich cathode Li1.2Co0.8O2 for high capacity and excellent cycling performance. This work provides theoretical insights into the effects of CSRD on LiCoO2 and Li-rich cathodes for rational design and synthesis.

Laboratory-Scale Natural Gas Hydrate Extraction Numerical Simulation Under Phase Transition Effect

Phase transition in gas hydrate reservoirs has a significant effect on the fluid flow dynamic when performing test production, which should be carefully studied. This study systematically investigates the phase transition characteristics of natural gas hydrates during the depressurization extraction process through laboratory-scale numerical simulations. First, a laboratory-scale numerical simulation model is established with dimensions of 1 m × 1 m × 1 m. In the simulation, the nanoscale and microscale effect on phase transition is considered. Then, the analysis of how different sediment types and their properties affecting gas production dynamics is presented. The results show that hydrate dissociation and formation are significantly influenced by factors such as the pore scale, salinity, and water content. In particular, montmorillonite had the most significant effect, leading to a 525.25% increase in gas production, while the impact of silty soil was relatively smaller. The increase in salinity inhibited hydrate formation but promoted dissociation, resulting in a significant increase in gas production, especially when the salinity reached to 3.5%, where gas production increased by 590.21%. An increase in water content led to a significant decrease in production. Through monitoring temperature and pressure changes during the extraction process, the different physical fields are analyzed, providing important theoretical support and practical guidance for the efficient extraction of natural gas hydrates.

Modeling of shock wave loading FeO to 1000 GPa

Iron oxide, FeO, is one of the main rock-forming oxides. Research into its thermophysical properties under high-energy loading is necessary to construct an equation of state that is used in modeling the properties of Earth's mantle and core as well as other celestial bodies. The results of calculations of thermodynamic properties of FeO under shock compression up to 1000 GPa are presented. In the phase transition field, calculations for FeO are performed as a mixture of low- and high-pressure phases based on the assumption that components of the mixture are in thermodynamic equilibrium under shock wave loadings. The conditions at the wave front are expressed in Rankin–Hugoniot ratios that express conservation of mass, momentum, and energy. Conservation conditions for momentum and energy flow are written for the mixture overall, while conservation conditions for mass flow are written separately for each component. Supplementing the obtained expressions with the condition of equality of the component temperature values and the equations of state for each component, shock adiabatic curves for a heterogeneous material are obtained. This method allows us to accurately describe the shock-wave loading of FeO, including in the phase transition region. Verification of simulation results is carried out using data obtained from experiments and calculations by other researchers. The considered technique is useful for calculations of similarly complex materials.

Two 3D Rare-Earth Double Perovskite Materials Constructed with a Pair of Enantiomers.

Organic-inorganic hybrid chiral small-molecule materials combine the inherent properties of both components; however, studies integrating chirality with rare-earth double-perovskite materials are limited. In this work, we synthesized two enantiomers of three-dimensional (3D) hybrid rare-earth double-perovskites, [R-3-HDMP]2CsEu(NO3)6 (1) and [S-3-HDMP]2CsEu(NO3)6 (2), by reacting R-3-HDMP and S-3-HDMP (where 3-HDMP = 3-hydroxy-N,N-dimethylpyrrole) with CsNO3 and Eu(NO3)3 in a 2:1:1 ratio within an acidic solution. Both R-3-HDMPI and S-3-HDMPI crystallize in the chiral space group P212121 at room temperature, exhibiting a transition from SHG-on to SHG-off (SHG = second harmonic generation) upon heating and cooling. The temperature-dependent X-ray single-crystal diffraction analysis carried out on compound 1 and compound 2, before and after the phase transition, disclosed the transformation of their space groups from noncentrosymmetric to centrosymmetric. Additionally, the incorporation of rare-earth elements as hybrid B-site cations imparts exceptional fluorescence properties to the compounds. These materials effectively merge the unique characteristics of chiral molecules with the exceptional luminescence of double-perovskite structures, paving the way for innovative optical devices and advanced information processing technologies.

Bose-Einstein condensation in a rigidly rotating relativistic boson gas

We study the Bose-Einstein condensation (BEC) of a free Bose gas under rigid rotation. The aim is to explore the impact of rotation on the thermodynamic quantities associated with BEC, including the Bose-Einstein (BE) transition temperature and condensate fraction. We begin by introducing the rotation in the Lagrangian density of free charged Klein-Gordon fields and determine the corresponding grand canonical partition function at finite temperature, chemical potential, and finite angular velocity. Assuming slow rotation, we derive analytical expressions for the pressure, energy, number, and angular momentum densities of a free Bose gas in nonrelativistic and ultrarelativistic limits in terms of the corresponding fugacities. We then focus on the phenomenon of BEC. We calculate the critical temperature of BEC transition and the condensate fraction in a slowly rotating Bose gas including only particles. Our findings indicate that the critical exponent associated with the BE transition in a rotating gas is lower compared to that in a nonrotating Bose gas. We also determine the fugacity in a rotating Bose gas in the aforementioned limits and examine how rotation affects its temperature dependence, both below and above the critical temperature. By analyzing the behavior of heat capacity at these temperatures, we demonstrate that in a nonrelativistic Bose gas, the rotation transforms the nature of the BE phase transition from a continuous to a discontinuous transition. In general, we find that a nonrelativistic Bose gas under rotation behaves similarly to a nonrotating Bose gas in ultrarelativistic limit. Published by the American Physical Society 2025

Higher-order interactions induce stepwise explosive phase transitions

Higher-order interactions induce stepwise explosive phase transitions

Bridging measurement-induced phase transition and quantum error correction in monitored quantum circuits with many-body measurements

Bridging measurement-induced phase transition and quantum error correction in monitored quantum circuits with many-body measurements

Critical Energies and Wigner Functions of the Stationary States of the Bose Einstein Condensates in a Double‐Well Trap

AbstractThe quartic double‐well potential contains the essential ingredients to study many‐body systems within a rich semiclassical phase‐space that includes an unstable point associated to the critical energy. This critical energy in the quantum realm causes symmetry breaking of the wavefunctions and produces a logarithmic divergence in the density of states, leading to an excited‐state quantum phase transition (ESQPT). On the other hand, the Bose–Einstein Condensates (BEC) represent a promising platform to observe quantum mechanical phenomena at a macroscopic level. In this work, the lowest stationary states of the BEC in the mean field approximation are obtained via the Gross–Pitaevskii equation in a double‐well trap. The critical energy at which the corresponding wavefunctions experience the symmetry breaking is estimated. It is also found that this critical energy is shifted from the local maximum of the trap as the interaction between bosons increases. The Wigner function is used to obtain a phase space representation of the stationary states. It is observed that the state with closest mean energy to its critical value shows vestiges of the separatrix in the semiclassical phase‐space. The trends of the entropy, the nonorthogonality of the stationary states, and the nonclassicality via the negativities of the Wigner function are also examined.

Tuning of parity-time symmetry effect through exceptional points in non-Hermitian terahertz metasurface

In this article, we investigate parity-time (PT) symmetry in a non-Hermitian terahertz metasurface composed of two orthogonally oriented split ring resonators. Initially, one resonator is diagonally displaced relative to the other to study PT-symmetry in the system. The eigenvalues and eigenstates of the metasurface are examined at various displacement values to analyze the PT-symmetric phase transition. At a specific displacement, the metasurface design exhibits degenerate eigenvalues, marking the occurrence of an exceptional point. Beyond this point, the system transitions into a broken PT-symmetry phase. PT-symmetry is further explored by displacing the second resonator vertically and horizontally. This investigation reveals the presence of exceptional points during the transition from PT-asymmetry to PT-symmetry states. Additionally, the role of the split gap in the second resonator relative to the first is analyzed in this non-Hermitian system. It is observed that near-field coupling between the resonators plays a significant role during displacement. This is supported by the application of coupled mode theory to the metasurface. This comprehensive study on the impact of resonator displacement leading to exceptional points in a strongly coupled system holds potential for highly sensitive sensing applications and other advancements in photonics.

Sustainable thermal buffering of microencapsulated bio-phase change materials through an engineered biochar dopant

Abstract Climate change and unbalanced energy demand and consumption require innovative approaches to the development of sustainable and renewable energy technologies. Phase change materials (PCMs) present exceptional solutions for zero-energy thermal management due to their outstanding energy storage density at an isothermal phase transition. However, the low thermal transport and thermal stability of bulk PCMs, as well as the expensive and complex synthesis of additive materials, hinder their large-scale utilization. In this study, food-waste-derived engineered biochar (FW) is produced via slow pyrolysis to improve the thermal properties of a microencapsulated bio-PCM (B28). The thermal performance of biochar-PCM composites is evaluated based on two biochar preparation systems: varying activation temperatures (carbonized at 400 °C followed by KOH activation at different temperatures (500–800 °C)) and varying mass ratios between KOH and biochar. The introduction of a low (0.63 wt%) engineered biochar dopant significantly improves the thermal diffusivity of B28 by more than 1.3-fold. The biochar-PCM microcapsule composites present fusion and crystalline isothermal phase transition temperatures of 29.4 ± 0.38 °C and 16.7 ± 0.13 °C, respectively. Moreover, the bio-PCM exhibits a highly efficient energy per unit mass of 61.6 kJ kg–1, which is 101.7% of the energy storage capacity of bulk B28. Additionally, the composite demonstrates high thermal stability with decomposition occurring above 195 °C, thus enabling an increase of > 20 °C in the onset decomposition point compared with pristine B28. Further analysis reveals the impact of the KOH/biochar mass ratio on the thermal properties of bio-PCM. Sample FW6PCM, in which the biochar is activated at 600 °C with a KOH/biochar mass ratio of 1, exhibits the highest enthalpy storage capacity. This study suggests a promising strategy for designing high-performance, eco-friendly, and scalable bio-based composite PCMs by overcoming the long-standing bottleneck of microcapsules, which is crucial for advanced thermal management applications such as cooling and green buildings. Graphical Abstract

Sustained Delivery of Liraglutide Using Multivesicular Liposome Based on Mixed Phospholipids

Background: Although peptides are widely used in the clinical treatment of various diseases due to their strong biological activity, they usually require frequent injections owing to their poor in vivo half-life. Therefore, there is a strong clinical need for sustained peptide formulations. Methods: In this study, liraglutide (Lir) and biocompatible multivesicular liposomes (MVLs) were utilized as the model drug and sustained-release carriers, respectively. The drug release rate of Lir-MVLs was controlled by changing the ratio of SPC and DEPC with different phase transition temperatures (PTT, PTTSPC = −20 °C, PTTDEPC = 13 °C). Results: As the SPC ratio increased, Lir-MVLs had more flexible lipid membranes, poorer structural stabilization, and fewer internal vesicles with larger particle sizes, contributing to faster release of Lir. After subcutaneous injection of Lir-MVLs, the blood glucose concentration (BGC) of db/db mice decreased to different levels. When the SPC-DEPC ratio was greater than 85:15, the drug release rate was too fast; the BGC remained below 16 mM for only 2–4 days, while when the drug release rate was too slow, was the case when the SPC-DEPC ratio was less than 50:50, the BGC also remained below 16 mM for only 2–3 days. However, when the SPC-DEPC ratio was 75:25, the BGC could be maintained below 16 mM for 8 days, indicating that the release properties of this ratio best met the pharmacological requirements of Lir. Conclusions: This study investigated the effects of phospholipids with different PTT on the release characteristics of Lir-MVLs, and provided ideas for the design of sustained-release peptide preparations.

FOIM: Thermal Foaming of Shape Memory Polyurethane Foil.

This work introduces the semi-finished product FOIM, a neologism from FOIl and foaM, a phase segregated polyester urethane urea (PEUU) foam, which is synthesized from poly(1,6-hexylene adipate) diol, 4,4'-methylene diphenyl diisocyanate, polyethylene glycol and water as blowing agent. The PEUU is obtained by following a one-shot synthesis and is characterized by a hard/soft segment ratio of 1.06 and an open pore content of 78%. Differential scanning calorimetry reveals a melting peak at 45°C and a crystallization signal at 14°C, both of which are associated with the phase transitions of the soft segment. The glass transition temperature, which is determined as a local maximum within the tanδ using dynamic mechanical analysis, is 1°C. During programming, the foam is heavily compressed at 60°C. Once unloaded at 23°C, a translucent foil, the FOIM, is obtained. When reheated to 60°C, the foil switches back to the foam due to its pronounced shape memory properties. Intriguingly, the structure remains largely unaffected by the drastic deformation as indicated by buoyancy and heat transmission measurements. The ease of manufacture and functionality makes the technology attractive for applications, in which both low transport volumes and drastic shape changes are desired.

Deconfinement and chiral restoration phase transition under rotation from holography in an anisotropic gravitational background

We investigate the effects of rotation on deconfinement and chiral phase transitions in the framework of the dynamical holographic QCD model. Instead of transforming to the rotating system by Lorentz boost, we construct an anisotropic gravitational background by incorporating the rotating boundary current. We first investigate the pure gluon system under rotation to extract deconfinement phase transition from the Polyakov loop then add two-flavor probe for chiral restoration phase transition from the chiral condensate. It is observed that at low chemical potentials, the deconfinement phase transition of pure gluon system is of first order and the chiral phase transition of a two-flavor system is of crossover. Both the critical temperatures of deconfinement and chiral phase transitions decrease/increase with imaginary/real angular velocity (ΩI/Ω) as T/Tc∼1−C2ΩI2 and T/Tc∼1+C2Ω2, which is consistent with lattice QCD results. In the temperature-chemical potential T−μ phase diagram, the critical end point moves toward regions of higher temperature and chemical potential with real angular velocity. Published by the American Physical Society 2025

Geometric meaning of high-order exceptional points in non-Hermitian Su–Schrieffer–Heeger model

Abstract We investigate the geometric meaning of high-order exceptional points (EPs) in non-Hermitian Su–Schrieffer–Heeger model. High-order EPs are highly associated with the non-Bloch parity-time ( PT ) symmetry, a novel type of PT symmetry caused by the non-Hermitian skin effect (NHSE). The bulk states arising from the NHSE possess higher-order EPs at the critical point of the non-Bloch PT phase transition. We also analyze the phase transition using the ratio of complex eigenenergies and employ saddle point theory to further clarify the geometric significance of higher-order EPs and non-Bloch PT phase transition. Finally, we generally prove that in an extended two-band non-Hermitian system, the values of generalized Brillouin zone at high-order EPs are zero or infinity. This work helps us further understand high-order EPs in nonreciprocal topological systems.

Evidence of Magnetocaloric Effect in (Fe63Ni37)89B11 Nanostructured Magnetic Alloys

Abstract The magnetocaloric effect associated with magnetic entropy changes (ΔS M ) and phase transitions in (Fe63Ni37)89B11 (FeNiB) powder alloys was investigated. For this purpose, the particle size of the samples was reduced under milling times of 0 (FNB) and 36 hours (FNB36). X-ray diffraction and Mössbauer spectroscopy results showed the formation of nanostructured magnetic alloys and the coexistence of γ-FCC, α-BCC, and oP-(Fe, Ni)B phases in agreement with the INVAR region. M(H) measurements revealed that both alloys are ferromagnetic soft at room temperature, with coercive field values below ~ 48 Oe. A detailed analysis of the magnetic phase transition using the modified Arrott plot and critical isotherm plots yields critical exponents (β = 0.27, γ = 0.92, and α = 4.4) close to the theoretical exponents obtained from the Tricritical Mean Field model. Moreover, a maximum magnetic entropy change (ΔS M ) was evidenced around the phase transition (T C ) at ~ 330 K (− ΔS M of 2.58 J kg−1 K−1) for FNB and ~ 415 K (− ΔS M of 0.4 J kg−1 K−1) for FNB36 with an applied field of 1.3 T. The relative cooling power and the temperature-averaged entropy change values were determined, and they exhibited a linear dependency as function of the external field. These findings give a good insight towards the advancements of FNB-based alloys for potential room-temperature magnetic refrigeration technology.

Phase transition extracted by Principal Component Analysis in the disordered Moore-Read state

Abstract We study the influence of disorder on the Moore-Read state by principal component analysis (PCA), which is one of ground state candidates for the 5/2 fractional Hall state. By using PCA, the topological features of the ground state wave functions with different disorder strengths can be distillated. And as the disorder strength increases, the Moore-Read state will be destroyed. We explore the phase transition by analyzing the overlaps between the random sample wave functions and the topologically distilled state. The cross-point between the amplitudes of the principal component and its counterpart is the phase transition point. Additionally, the origin of the second component comes from the excited states, which is different from the Laughlin state.

Short and long-range magnetic ordering and emergent topological transition in (Mn1−xNix)2P2S6

Two-dimensional magnetic materials with tunable physical parameters are emerging as potential candidates for topological phenomena as well as applications in spintronics. The famous Mermin-Wagner theorem states that spontaneous spin symmetry cannot be broken at finite temperature in low dimensional magnetic systems which forbids the possibility of a transition to a long-range ordered state in a two-dimensional magnetic system at finite temperature. Though, there are some exceptions to Mermin-Wagner theorem in particular low dimensional magnetic systems with topologically ordered phase transitions. Here, we present an in-depth temperature dependent analysis for the bulk single crystals of two-dimensional (Mn1−xNix)2P2S6 with x = 1, 0.7, 0.3, 0 using the Raman spectroscopy supported by first-principles calculations of the phonon frequencies. We observed multiple phase transitions with tunability as a function of doping associated with the short and long-range spin-spin correlations. First transition at ~ 150 K to ~ 170 K for x = 0 to x = 0.7, and second one from ~ 60 K to ~ 153 K. Quite interestingly, a third transition is observed at low temperature (much below their respective TN) ~ 24 K to ~ 60 K and is attributed to the potential topological phase transition. These transitions are marked by the distinct changes observed in the temperature evolution of the phonon self-energy parameters, modes intensity and dynamic Raman susceptibility.

Controlling the Mott–Peierls transition in epitaxial VO2 (M1) film grown by PLD for near-IR photodetection

Vanadium dioxide (VO2) (M1) exhibits a unique metal–insulator transition (MIT) near room temperature, garnering considerable attention for its applications in bolometer, terahertz/infrared detectors, and microelectronic devices. Here, we explore the potential of epitaxially grown VO2 (M1) thin films for near-infrared (IR) detection by optimizing the growth conditions, followed by structural characterization and device fabrication. Alongside the VO2 (M1) phase, two other oxides from the vanadium oxide family, VO2 (A) and V2O5, were also grown on a c-cut sapphire substrate using a pulsed laser deposition (PLD) system. In-depth analysis using temperature-dependent XRD and Raman spectroscopy confirmed the crystalline structure and the quality of epitaxial thin film formation of VO2 (M1), while also unveiling structural phase transition (SPT) behavior and the critical temperature of transition. At elevated temperatures during electrical measurement, the VO2 (M1) epilayer exhibits a first-order phase transition from the metallic to the insulating state, accompanied by a significant change in resistance exceeding three orders of magnitude unveiling its potential in thermal switches, memory-based devices etc. In depth, electrical analysis on all the grown oxides shows that VO2 (M1) and V2O5 exhibit a higher temperature coefficient of resistance (TCR) (3%/K and 2%/K) and a lower 1/f noise (in the order pA/Hz at 0.1 Hz) as compared to VO2 (A), paving scope for further analysis of these two oxides toward important applications in the domain of thermal sensors. Additionally, VO2 (M1) exhibited good bolometric response (in the order of ms) to IR radiation, proving its candidature for the application in IR detectors as well.

Myocardia-Injected Synergistically Anti-Apoptotic and Anti-Inflammatory Poly(amino acid) Hydrogel Relieves Ischemia-Reperfusion Injury.

Reperfusion therapy is the most effective treatment for acute myocardial infarction, but its efficacy is frequently limited by ischemia-reperfusion injury (IRI). While antioxidant and anti-inflammatory therapies have shown significant potential in alleviating IRI, these strategies have not yielded satisfactory clinical outcomes. For that, a thermo-sensitive myocardial-injectable poly(amino acid) hydrogel of methoxy poly(ethylene glycol)45-poly(L-methionine20-co-L-alanine10) (mPEG45-P(Met20-co-Ala10), PMA) loaded with FTY720 (PMA/FTY720) is developed to address IRI through synergistic anti-apoptotic and anti-inflammatory effects. Upon injection into the ischemic myocardium, the PMA aqueous solution undergoes a sol-to-gel phase transition and gradually degrades in response to reactive oxygen species (ROS), releasing FTY720 on demand. PMA acts synergistically with FTY720 to inhibit cardiomyocyte apoptosis and modulate pro-inflammatory M1 macrophage polarization toward anti-inflammatory M2 macrophages by clearing ROS, thereby mitigating the inflammatory response and promoting vascular regeneration. In a rat IRI model, PMA/FTY720 reduces the apoptotic cell ratio by 81.8%, increases vascular density by 34.0%, and enhances left ventricular ejection fraction (LVEF) by 12.8%. In a rabbit IRI model, the gel-based sustained release of FTY720 enhanced LVEF by an additional 7.2% compared to individual treatment. In summary, the engineered PMA hydrogel effectively alleviates IRI through synergistic anti-apoptosis and anti-inflammation actions, offering valuable clinical potential for treating myocardial IRI.